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  • 1
    Language: English
    In: Journal of Soils and Sediments, 2012, Vol.12(1), pp.75-85
    Description: Byline: Gawan Jacob Hilma Muehl (1), Joerg Ruehlmann (1), Marc-Oliver Goebel (2), Joerg Bachmann (2) Keywords: Film; Fluorescence; Porous media; Segmentation; Visualization; Wettability Abstract: Purpose Wettability affects water configuration and thereby transport processes and microbial activity in soil. Approaches to visualize the effect of porous media wettability on water films surrounding particles are rarely available in the literature. The aim of this study is therefore (1) to visualize the effect of wettability on area and connectivity of the water phase and (2) to develop a segmentation strategy to enable water films and bulk water to be differentiated. Materials and methods Wettability of silica sand was rendered by silanization using dichlorodimethylsilane. The resulting contact angle was measured using the sessile drop method. Furthermore, wettability was characterized by the water penetration time test in air-dry samples and at a volumetric water content of 8 vol.%. Sulforhodamine B was used to stain distilled water at a concentration of 40 mg/l. By means of the Wilhelmy plate method, the influence of the dye on the liquid surface tension was tested. Confocal laser scanning microscopy (CLSM) was used to visualize the area and connectivity of the fluorescent-dyed water phase and the thickness of water films in untreated and silanized samples at water contents of 8, 16, and 32 vol.%. Results and discussion The silanization significantly increased the contact angle of silica sand, whereas the surface tension of the dye solution did not differ significantly from that of undyed water. CLSM visualized the distribution of water, focused across the surface grain layer. Thresholding of fluorescence signal in two-dimensional intensity projections enables the discrimination between film and bulk water. It was shown that even subcritical water repellency (contact angle 〈90) leads to a decrease in area and connectivity of the water phase by affecting film instead of bulk water. CLSM detects decreasing effects of wettability with increasing water content, which were no longer significant at a water content of 32 vol.%. CLSM was found to be more sensitive for detecting the effects of wettability than the water drop penetration time test. Conclusions CLSM provides new insight into wettability-dependent water configuration. One advantage over conventional microscopy arises from the capability to visualize water focused over the pore space. Compared to other three-dimensional imaging techniques, the advantage of CLSM is its simplicity. If only the optically accessible upper layer of the porous media is of interest, sample preparation, measurements, and image analysis can easily be carried out with a cost- and time-saving setup. Author Affiliation: (1) Institute of Vegetable and Ornamental Crops Grossbeeren/Erfurt, Theodor-Echtermeyer-Weg 1, 14979, Grossbeeren, Germany (2) Institute of Soil Science, Leibniz University of Hannover, Herrenhauser Str. 2, 30419, Hannover, Germany Article History: Registration Date: 29/06/2011 Received Date: 02/03/2011 Accepted Date: 27/06/2011 Online Date: 04/08/2011 Article note: An erratum to this article can be found at http://dx.doi.org/10.1007/s11368-011-0422-8
    Keywords: Film ; Fluorescence ; Porous media ; Segmentation ; Visualization ; Wettability
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 2
    Language: English
    In: Journal of Soils and Sediments, 2012, Vol.12(1), pp.116-116
    Description: Byline: Gawan Jacob Hilma Muehl (1), Joerg Ruehlmann (1), Marc-Oliver Goebel (2), Joerg Bachmann (2) Author Affiliation: (1) Institute of Vegetable and Ornamental Crops Grossbeeren/Erfurt, Theodor-Echtermeyer-Weg 1, 14979, Grossbeeren, Germany (2) Institute of Soil Science, Leibniz University of Hannover, Herrenhauser Str. 2, 30419, Hannover, Germany Article History: Registration Date: 22/08/2011 Online Date: 06/09/2011 Article note: The online version of the original article can be found at http://dx.doi.org/10.1007/s11368-011-0395-7.
    Keywords: Environment ; Environmental Physics ; Soil Science & Conservation ; Environment, General ; Agriculture;
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 3
    Language: English
    In: Catena, November 2017, Vol.158, pp.46-54
    Description: Aggregate stability (AS) is an important property controlling erodibility of volcanic ash soils and is known to be strongly affected by fine-grained iron (Fe) and aluminum (Al) minerals. Assuming that frequency dependence of magnetic susceptibility (MS) is related to the amount of fine-grained Fe minerals and considering that formation of fine-grained Fe and Al minerals is closely coupled in volcanic ash soils, we hypothesized that the measurement of MS can be used to evaluate AS of these soils. To verify this, we investigated volcanic ash soils along a 120-km transect in southern Chile, reaching from the Andean Southern Volcanic Zone (SVZ) to the Pacific coastal range. Stability of 1-cm macroaggregates from topsoil (0–5 cm) and subsoil (20–25 cm) was determined by wet-sieving, combining long-term water immersion and subsequent ultrasonic treatment. MS was measured at 465 and 4650 kHz to calculate its frequency dependence. We found an increasing amount of organic matter, fine-grained Fe and Al minerals, and clay and decreasing bulk density with increasing distance from the SVZ, indicating progressing soil development along the transect. Likewise, AS increased with increasing distance from the SVZ and was found to be controlled primarily by soil organic matter and fine-grained Fe and Al minerals. While MS itself showed only slight variation, its frequency dependence continuously increased with increasing distance from the SVZ, indicating an increasing fraction of fine-grained ferrimagnetic particles. Accordingly, frequency dependence of MS was found to be linearly related to the amount of fine-grained Fe minerals as quantified by dithionite extraction, and moreover, due to the close linear relationship between fine-grained Fe and Al phases, it revealed to be suitable for estimating the total amount of both fine-grained Fe and Al minerals. Analysis of underlying material (60–65 cm) indicated that the increase in frequency dependence of MS with increasing distance from the SVZ was caused by fine-grained ferrimagnetic particles of pedogenic and lithogenic origin. Although overall organic matter content turned out to be more closely related to the stability of the investigated aggregates, we conclude that frequency dependence of MS can be used as an easily obtainable proxy for assessing the contribution of fine-grained Fe and Al minerals to AS.
    Keywords: Andosols ; Iron Oxides ; Magnetic Susceptibility ; Mineral Magnetism ; Pedogenesis ; Soil Aggregate Stability ; Sciences (General) ; Geography ; Geology
    ISSN: 0341-8162
    E-ISSN: 1872-6887
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  • 4
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 2017, Vol.180(3), pp.279-282
    Description: We investigated glucose‐6‐phosphate (G6P) release from ferrihydrite by ligand‐promoted dissolution by oxalate, ascorbate, and desferrioxamine‐B in comparison to orthophosphate (OP). Overall, P release was poorly related to Fe dissolution. Initial release of G6P was higher as compared to OP, likely due to its preferential adsorption at outer surface sites caused by pore size effects. Our data suggest that G6P is potentially more bioavailable (., mobilizable) than OP.
    Keywords: Bioavailability ; Iron Oxides ; Mineral‐Associated Phosphorus ; Organic Acids ; Organic Phosphorus ; Siderophores
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 5
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 2016, Vol.179(6), pp.799-808
    Description: The drying process of volcanic ash soils often results in the formation of shrinkage cracks with consequences for their physical properties (., decrease of water retention capacity) and land use management. This study presents the soil water characteristics and shrinkage behaviour (shrinkage phases in terms of void and moisture ratio), the shrinkage potential (COLE index), and the pore shrinkage capacity (PSI) for 5 and 20 cm depth of a Haplic Arenosol (tephric) and two Silandic Andosols under pasture management along a soil gradient from the Andean mountains to the coastal range in southern Chile. The main focus of the presented study is on the effect of soil development in conjunction with the weathering of volcanic ash soils on the shrinkage properties. The water retention and shrinkage curves were continuously determined for undisturbed soil samples (100 cm) during a drying process under laboratory conditions. In addition, the shrinkage curve data were modelled to distinguish different shrinkage zones. The results suggest that the investigated soil properties vary depending on soil development. The more developed Andosols had higher total porosities (up to 70 cm cm) than the less developed Arenosol. The shrinkage behaviour of the Haplic Arenosol showed a wide structural shrinkage phase, whereas the Silandic Andosols revealed a more pronounced proportional shrinkage phase, which is related to the pore size distribution. In addition, wide and narrow coarse pores of the Haplic Arenosol and medium and fine pores of the Silandic Andosols determine the shrinkage potential (COLE) and the pore shrinkage capacity, respectively. The finer‐grained and organic matter‐rich Andosols indicate a higher COLE index (〉 0.03–0.09) compared to the Arenosol (≤ 0.03). The pore shrinkage index (PSI) of the total pores (TP) varied significantly ( 〈 0.05) with values of 0.042–0.149 in 5 cm depth and 0.04–0.091 in 20 cm depth of sites 1–3, respectively.In summary, the shrinkage potential and pore shrinkage capacity are positively correlated to the organic carbon content and decrease with increasing dry bulk density. The study points out a higher risk of soil degradation due to irreversible drying processes for the more clayey and allophane containing Andosols than the Arenosol.
    Keywords: Southern Chile ; Andosol ; Arenosol ; Soil Water Retention ; Shrinkage Potential ; Pore Shrinkage Capacity
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 6
    Language: English
    In: Ecosystems, 2018, Vol.21(2), pp.280-296
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s10021-017-0148-6 Byline: Ina Christin Meier (1), Florian Knutzen (1), Lucia Muriel Eder (1,2,4), Hilmar Muller-Haubold (1), Marc-Oliver Goebel (3), Jorg Bachmann (3), Dietrich Hertel (1), Christoph Leuschner (1) Keywords: coarse roots; European beech; fine roots; mature trees; optimal partitioning theory; precipitation gradient; rooting depth; root morphology; root-to-shoot ratio Abstract: Abstract When applied to climate change-related precipitation decline, the optimal partitioning theory (OPT) predicts that plants will allocate a larger portion of carbon to root growth to enhance the capacity to access and acquire water. However, tests of OPT applied to the root system of mature trees or stands exposed to long-term drying show mixed, partly contradicting, results, indicating an overly simplistic understanding of how moisture affects plant-internal carbon allocation. We investigated the response of the root system (0--240 cm depth) of European beech to long-term decrease in water supply in six mature forests located across a precipitation gradient (855--576 mm mean annual precipitation, MAP). With reference to OPT, we hypothesized that declining precipitation across this gradient would: (H1) cause the profile total of fine root biomass (FRB roots 〈2 mm) to increase relative to total leaf mass (H2) trigger a shift to a shallower root system and (H3) induce different responses in the depth distributions of different root diameter classes. In contradiction to H1, neither total FRB (0--240 cm) nor the FRB:leaf mass ratio changed significantly with the MAP decrease. The support for H2 was only weak: the 95% rooting depth of fine roots decreased with decreasing MAP, whereas the maximum extension of small coarse roots (2--5 mm) increased, indicating contrasting responses of different root diameter classes. We conclude that long-term decline in water supply leads to only minor adaptive modification with respect to the size and structure of the beech root system, with notable change in the depth extension of some root diameter classes but limited capacity to alter the fine root:leaf mass ratio. It appears that OPT cannot adequately predict C allocation shifts in mature trees when exposed to long-term drying. Graphical Abstract Author Affiliation: (1) 0000 0001 2364 4210, grid.7450.6, Plant Ecology, Albrecht von Haller Institute for Plant Sciences, University of Goettingen, 37073, Goettingen, Germany (2) 0000 0004 1936 9756, grid.10253.35, Soil and Hydraulic Geography, Faculty of Geography, University of Marburg, 35032, Marburg/Lahn, Germany (3) 0000 0001 2163 2777, grid.9122.8, Institute for Soil Science, University of Hannover, 30419, Hannover, Germany (4) 0000 0004 0491 7318, grid.419500.9, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany Article History: Registration Date: 08/04/2017 Received Date: 23/02/2016 Accepted Date: 28/03/2017 Online Date: 08/05/2017 Article note: Author Contributions CL, ICM, and DH conceived of or designed the research project. FK, MOG, LME, and HMH performed research. ICM analyzed the data. ICM, CL, MOG, and JB wrote the manuscript. Electronic supplementary material The online version of this article (doi:10.1007/s10021-017-0148-6) contains supplementary material, which is available to authorized users.
    Keywords: coarse roots ; European beech ; fine roots ; mature trees ; optimal partitioning theory ; precipitation gradient ; rooting depth ; root morphology ; root-to-shoot ratio
    ISSN: 1432-9840
    E-ISSN: 1435-0629
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  • 7
    Language: English
    In: Environmental Chemistry, 2014, Vol.11(6), p.709-718
    Description:  The supramolecular structure and resulting physicochemical properties of soil organic matter (SOM) significantly control storage and buffer functions of soils, e.g. for nutrients, organic molecules and water. Multivalent cations, able to form complexes, are suggested to form inter- and intramolecular cross-links in SOM. At present, specific effects of the valence and type of cation on SOM properties are incompletely understood. We investigated changes in SOM interfacial properties, its ability to release mobile colloids in aqueous solutions and its sorption affinity towards organic chemicals in dependence on cation–SOM interactions, temperature and aging time.
    Keywords: colloids; contact angle; sorption; X-ray photoelectron spectroscopy.
    ISSN: 1448-2517
    E-ISSN: 1449-8979
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  • 8
    Language: English
    In: 한국토양비료학회 학술발표회 초록집, 2014, Vol.2014(6), pp.209-209
    Keywords: Surface Chemistry ; Xps ; Contact Angle
    Source: DBpia - 디비피아 (Nurimedia)
    Source: DBpia (Nurimedia)
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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, 2004, Vol.167, pp.685-692
    Keywords: Sciences of the Universe ; Other ; Agriculture ; Biology ; Botany
    ISSN: 1436-8730
    E-ISSN: 1522-2624
    Source: Hyper Article en Ligne (CCSd)
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  • 10
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 2004, Vol.167(6), pp.685-692
    Description: Aliphatic C most probably derived from ester‐bound moieties was found to be present in sandy subsoil horizons. The hydrophobic nature of such compounds may increase their stabilization potential. Therefore, the aim of this study was to investigate the potential of aliphatic compounds in mineral soil horizons along a Dystric Cambisol profile under beech forest to increase hydrophobicity. The conceptual approach included the analyses of soil samples before and after solvent extraction and base hydrolysis for elemental and isotopic composition. Additionally, the advancing contact angle was measured to quantify hydrophobicity. Curie‐point pyrolysis GC/MS was carried out to characterize the nature of alkyl C present in subsoil samples. A close correlation between the C activity and the stable‐C‐isotope ratio (δC) indicates isotopic fractionation upon C stabilization in subsoils. Free lipids contributed less than 10% to the organic C found in subsoil horizons. Base hydrolysis revealed very high amounts of hydroxyalkanoic acids in the B horizons of the acid forest soil. Hydrophobicity of SOM was not found to be correlated to esterified‐ or free‐lipid content. The contact angle was in a similar range for all bulk soil horizons, suggesting greater hydrophobicity of organic matter in subsoil horizons considering their very low concentrations of organic C compared to the A horizon. The quantity and nature of pyrolysis products change with increasing depth in the soil profile. Aliphatic products cannot be detected in B and C horizons by Curie‐point pyrolysis GC/MS. Alkyl‐C und Hydrophobizität in B‐ und C‐Horizonten eines sauren Waldbodens In den Horizonten sandiger Unterböden kommt es zur Anreicherung aliphatischer Substanzen, die vermutlich estergebunden sind. Die hydrophobe Natur dieser Verbindungen könnte ihre Stabilisierung gegenüber mikrobiellem Abbau begünstigen. Das Ziel unserer Arbeiten war es, zu untersuchen, ob aliphatische Verbindungen die Hydrophobizität organischer Substanzen im Bodenprofil einer sauren Braunerde unter Buche erhöhen können. Hierzu wurde die Element‐ und Isotopenzusammensetzung von Bodenproben vor und nach Lipidextraktion sowie basischer Hydrolyse untersucht. Zusätzlich wurden Kontaktwinkelmessungen zur Quantifizierung der Hydrophobizität durchgeführt. Curie‐Punkt‐Pyrolyse‐GC/MS wurde angewandt, um die Zusammensetzung des Alkyl‐C zu charakterisieren. Eine Korrelation zwischen der C‐Aktivität und dem Verhältnis der stabilen C‐Isotope (δC) zeigt, dass es während der C‐Stabilisierung zu einer Isotopenfraktionierung kommt. Freie Lipide machten weniger als 10 % des organischen C in den Unterbodenhorizonten aus. Die basische Hydrolyse zeigte hohe Anteile von Hydroxyalkansäuren in den B‐Horizonten des sauren Waldbodens. Die Hydrophobizität der organischen Substanz war nicht mit dem Gehalt an freien und/oder gebundenen Lipiden korreliert. Der Kontaktwinkel zeigte in allen Bodenhorizonten ähnliche Werte, so dass für die organische Substanz in den Unterbodenhorizonten mit ihren im Vergleich zu den A‐Horizonten sehr geringen C‐Gehalten eine größere Hydrophobizität angenommen werden muss. Die Anzahl und chemische Zusammensetzung der Pyrolyseprodukte veränderte sich mit zunehmender Profiltiefe. Aliphatische Verbindungen konnten mit Curie‐Punkt‐Pyrolyse in den B‐ und C‐Horizonten nicht nachgewiesen werden.
    Keywords: Alkyl Carbon ; Subsoil ; Hydrophobicity
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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